1. Field of the Invention
Flexible cold-cure polyurethane foams are known for use in a broad range of applications, and are used in the furniture and motor car industries. Where they are used as seat cushions or back rests, the resilience or damping action of the foam is an important factor. It is for this reason that resilience indices are specified for particular foam components.
Particularly resilient foam qualities are generally regarded as comfortable. Damping foams have the advantage that vehicle vibration is either not transmitted to the occupants, or is transmitted only in a weakened form. It is for these two reasons that it is desirable to be able to tailor the resilience of the foam for a motor car seat precisely to the requirements of the motor car manufacturer.
2. Description of the Prior Art
Processes for increasing damping action are known and are used as appropriate. A modification to the cellular structure, making it finer and more uniform, has the effect of increasing damping action. The damping action may also be increased, or the resilience reduced, by chemical means. One possibility is to add polyethers with OH numbers greater than 200 in proportions of from 5 to 25 wt-% of the total polyol component. A further possibility is to use methylenebis(phenyl isocyanates) ("MDI") on the isocyanate side instead of tolylene diisocyanate ("TDI") or modified TDI. The superior damping action provided by MDI (in comparison to TDI) has been regarded as especially advantageous.
The use of polyethers containing more than 50 wt-% of ethylene oxide in cold foam formulations is generally known. The usual quantity used (based upon the total quantity of polyether) is, however, less than 3 wt-%. In this function the polyethers are known as "cell openers". If concentrations in excess of 5 wt-% of polyether having an ethylene oxide content greater than 50 wt-% are used in typical cold-molded foam formulations, unstable or collapsing foams result.
Use of polyethers having an ethylene oxide content greater than 50 wt-% in cold foam formulations is described, for example, in German Offenlegungschrift 3,721,058, although in the latter case water quantities in excess of 5 wt-% are used. Foams prepared in this manner do not excel in terms of their high resilience; their character is much more that of damping. The stability of these foams is achieved by means of extremely low indices.
The use or addition of polyethers having an ethylene oxide content greater than 50 wt-% is also known for molded hot cure polyurethane flexible foams, as described, e.g., in German Offenlegungschrift 3,903,100. However, molded hot-cured foams are normally prepared with different raw materials (e.g., polyethers having only a maximum of 50% primary OH groups, pure TDI as isocyanate, stabilizers which exert a marked closing action, and incorporation of organometallic catalysts) than those used for molded cold-cure foam. The different type of basic raw materials and the special processing technology cause a different level of values in the resulting foams. Hot foam, for example, does not reach the high resilience values which distinguish molded cold-cure foam. In particular, the addition of polyethers having ethylene oxide contents greater than 50 wt-% in the polyol component does not, for hot foams have a destabilizing effect on the resulting foam. Also, the high resilience values, which result with cold foams, are not achieved.